Aspects of Stability and Phenomenology in Type IIA Orientifolds with Intersecting D6-branes

TL;DR

This paper explores the stability, phenomenology, and model-building aspects of Type IIA orientifolds with intersecting D6-branes, including tadpole conditions, spectrum analysis, and potential inflation scenarios.

Contribution

It provides detailed constructions of stable non-SUSY and SUSY models, including a flipped SU(5) GUT and a Pati-Salam model, using complex structures and fractional D-branes.

Findings

Stable non-SUSY 3-generation model from a Z_3-orbifold

Explicit Pati-Salam model with potential MSSM breaking

Inflation driven by moduli is only feasible under specific conditions

Abstract

Intersecting branes have been the subject of string model building for several years. This work introduces in detail the toroidal and Z_N-orientifolds, where the main discussion employs the picture of intersecting D6-branes. The derivation of the R-R and NS-NS tadpole cancellation conditions in CFT is shown in detail. Various aspects of the massless spectrum are discussed, involving spacetime anomalies, the generalized Green-Schwarz mechanism and possible gauge breaking mechanisms. Both N=1 SUSY and non-SUSY approaches to low energy model building are treated. Firstly, the problem of complex structure instabilities in toroidal OmegaR-orientifolds is approached by a Z_3-orbifolded model, including a stable non-SUSY 3-generation standard-like model. It descends naturally from a flipped SU(5) GUT. Secondly, supersymmetric models on the Z_4-orbifold are discussed, involving exceptional 3-cycles and the explicit construction of fractional D-branes. A three generation Pati-Salam model that even can be broken down to a MSSM-like model is constructed as an example, involving non-flat and non-factorizable branes. Finally, the possibility that unstable closed and open string moduli could play the role of the inflaton is being explored. In the closed string sector, the slow-rolling requirement can only be fulfilled for very specific cases, where some moduli are frozen and a special choice of coordinates is taken. In the open string sector, inflation is not possible at all.